Double-blind, placebo-controlled clinical trial of preseasonal treatment with allergenic extracts of Olea europaea pollen administered sublingually.

In a double-blind, placebo-controlled, pilot clinical trial we evaluated the clinical efficacy and safety of immunotherapy (IT) with an extract of the pollen of the tree Olea europaea administered sublingually. The parameters tested were symptom score, dose-response bioassay of skin prick test and specific IgE and IgG, and the absolute value at a single serum dilution of each IgG subclass. Fifteen patients allergic to this pollen with symptomatology of rhinitis and/or rhinoconjunctivitis were randomly allocated to the placebo group (6 patients) or to the extract group (9 patients). Immunotherapy was administered in a short preseasonal period of time, practically no side effects being recorded. The group of patients treated with extract presented a slightly lower incidence (0.05 < p < 0.1) of nasal symptoms of sneezing and obstruction, and, more importantly, developed less dyspnea (p < 0.05) than the group treated with placebo, suggesting that IT can act as prophylaxis for the development of bronchial symptoms. No differences were observed in the immunological determinations. Differences in skin tests between the two groups displayed a slight significance (0.05 < p < 0.1) at the end of the trial; hence, a higher concentration of the allergen was needed in the group treated with extract to induce the same wheal as in the placebo group. In both groups the size of the wheal showed a time-dependent variation, which was dependent on the time of the year and independent of the type of treatment received, indicating a significant modification in the in vivo skin response to allergen challenge, demonstrated by a shift in the kinetics of allergen-ligand binding (slope) and in the magnitude of the measured response (intercept).